1. Field of the Invention
The present invention relates to storage control technology, and more particularly to storage virtualization technology.
2. Description of the Related Art
A technology disclosed in the abstract of Japanese patent Application Laid-Open No. 2005-266933 and in the abstract of Japanese patent Application Laid-Open No. 2004-227558, for example, is known in this field.
All sorts of storage virtualization technologies are known. The storage virtualization referred to herein is technology, which provides storage resources belonging to a storage subsystem existing externally to a storage control system (hereinafter, external storage subsystem) as though they are the storage resources of the storage control system. When a virtual storage resource is specified as the access destination, the storage control system issues an I/O command (input/output command) for either reading or writing data to an external storage subsystem, which has the storage resource corresponding to this specified storage resource.
When data is written or read as a result of the storage control system issuing an I/O command to an external storage subsystem, the external accessing takes time. Thus, the length of time of the I/O processing specified by the storage control system (for example, the length of time for processing an I/O command received from a host of the storage control system) increases. It is desirable to reduce this length of time.